Range finders based on laser techniques have been successfully developed as disclosed in U.S. Pat. Nos. 5,359,404, 5,612,779, and 5,574,552 granted to Laser Tech Co. A laser range finder employs a laser diode as its light source and can accurately determine the range of an object of interest at distances in excess of 1 Km. While laser range finders have found their way into numerous applications, they have proven to be extremely useful in military applications. In fact, laser range finders have been developed that are accurate to several meters of an object of interest.
A typical laser range finder includes a laser source, a laser receiver and a processor. In estimating the range of an object of interest, the laser source is directed at the object of interest and a series of laser pulses are emitted. The pulses strike the object of interest and are reflected. At least a portion of the reflected pulses travel back towards the laser range finder and are detected by the laser receiver. The detected pulses are provided to the processor, which then processes the detected pulses so as to estimate the distance between the laser range finder and the object of interest.
Presently, existing laser range finders have obtained accuracies within ±5 meters of an object of interest. There exists, however, a need for a laser range finder having better accuracies than are currently achievable. In particular, the military is requiring accuracies within ±3 meters. Moreover, these improved laser range finders must meet the weight and power constraints of the existing system architecture.
One proposed approach to improving the accuracy of existing laser range finders is to implement a low cost Analog-to-Digital Converter (hereinafter “ADC”) within the existing system architecture. The ADC is used to obtain an estimate of the reflected laser pulse signal intensity, which is then used to correct for range errors due to threshold detection. A drawback to this approach, however, is that since the target return intensities are unknown, due in part to the Gaussian structure of the pulses emitted by conventional laser sources, utilizing existing processing techniques would result in the need to employ an ADC with a very large dynamic range or several ADC's scaled to cover the range of potential intensities of the reflected laser pulses. An ADC with a large dynamic range will add significant cost to the system. Multiple ADC's present cost, power consumption and weight issues. Accordingly, neither approach meets the objectives described above.
Therefore, there is a need in the art to develop an enhanced laser range finder that improves range accuracy and performs within the design constraints of existing laser range finders. More particularly, there is a need in the art to develop a laser range finder that can employ a single low cost ADC, which can be used to effectively estimate the intensity of the reflected laser pulses, thereby enabling an accurate range calculation of an object of interest.